Transformer Protection Relays (Buchholz Principle) - EMB Gmbh

2. Design features
Casing
The casing is made of weather-resistant cast
aluminium alloy provided with a paint coat.
It is supplied either with screwed or flanged
connection (1). The different casing designs
available are shown in section 5 for singlefloat
Buchholz relays and section 7 for doublefloat
Buchholz relays, others are available on
request.
To check the switching system for proper
function, the casing is provided with sightglasses
(2). The sightglasses provided with scales
permit reading of collected gas volume.
The relays can be provided with hinged lids (3)
to protect the sightglasses.
Cover
The upper section of the cover accommodates
the terminal box (1). The test valve (2) and
the test key covered by a cap nut (3) as well
as a plate with instructions for actuating the
test key (4) are arranged in front of the cover.
The terminal box (1) accommodates the earth
terminal (5) and up to eight bushings (6) for
the terminals provided in the base of the cover.
The number of these bushings determines the
design of the switching systems in terms of
type and quantity of the magnet contact tubes.
The terminal box (1) is sealed by an aluminium
cap (7) so that it is safe to touch and protected
against pollution. If the cap is opened the graphic
symbol and the connection diagram (8)
are shown. The cable can be inserted through
the cable gland (9).
1
3
2
1
7
8
9
5
6
1
2
3
4
Figure 3 - Casing with flanged connection
Figure 4 - Casing with threaded connection
Figure 5 - Cover with cap removed
5